Comparison of survival and cost-effectiveness between unicondylar arthroplasty and total knee arthroplasty in patients with primary osteoarthritis - A follow-up study of 50,493 knee replacements from the Finnish Arthroplasty Register

Background and purpose Both unicondylar arthroplasty (UKA) and total knee arthroplasty (TKA) are commonly used for the treatment of unicompartmental osteoarthritis (OA) of the knee. The long-term survivorship and cost-effectiveness of these two treatments have seldom been compared on a nationwide level, however. We therefore compared the survival of UKA with that of TKA and conducted a cost-benefit analysis comparing UKA with TKA in patients with primary OA. Patients and methods We analyzed 1,886 primary UKAs (3 designs) and 48,607 primary TKAs that had been performed for primary OA and entered in the Finnish Arthroplasty Register between 1980 and 2003 inclusive. Results UKAs had a 60% (95% CI: 54-66) survival rate and TKAs an 80% (95% CI: 79-81) survival rate at 15 years with any revision taken as the endpoint. Overall survival of UKAs was worse than that of TKAs (p 0.001). All 3 UKA designs had poorer overall survival than the corresponding TKA designs. In the theoretical cost-benefit analysis, the cost saved by lower implant prices and shorter hospital stay with UKA did not cover the costs of the extra revisions. Interpretation At a nationwide level, UKA had significantly poorer long-term survival than TKA. What is more, UKA did not even have a theoretical cost benefit over TKA in our study. Based on these results, we cannot recommend widespread use of UKA in treatment of unicompartmental OA of the knee.